A turbine casing of a steam turbine is configured such that a low-pressure turbine casing and a high-pressure turbine casing are arranged in series and a rotor shaft bridges over each turbine casing. A bearing housing for supporting a heavy rotor shaft rotatably is provided integrally with or separately from the turbine casing. The bearing housing was originally formed integrally with the turbine casing. However, with growing size of a steam turbine plant, it is popular to provide the bearing housing separately from the turbine casing and to fix the bearing housing and the turbine casing separately to a concrete frame which functions as a foundation.
When installing the steam turbine plant, it is necessary to install and secure the bearing housing for supporting the heavy rotor shaft to the concrete frame with high-strength as well as installing and securing the turbine casing. Conventionally, the bearing housing was positioned and secured to the concrete frame in a direction perpendicular to the rotor shaft by means of a fixing hardware. Such securing apparatus for a steam turbine casing with which a bearing housing is formed integrally is disclosed in FIG. 3 and FIG. 4 of Patent Literature 1 and is explained here in reference to FIG. 8 and FIG. 9.
As shown in FIG. 8 and FIG. 9, a securing device 100 for a bearing housing is provided on a supporting surface 102a of a concrete frame 102 and spaces 103 and 104 are provided in line for housing the turbine casings. A high-pressure turbine casing is installed and secured to the space 104, whereas a low-pressure turbine casing is installed and secured to the space 103. FIG. 8 shows a low-pressure turbine outer casing (lower half) which is separated into two pieces 105a and 105b and the low-pressure turbine outer casing 105a and 105b is installed and secured to the space 104. The low-pressure turbine outer casing 105a and 105b is formed integrally with the bearing housing 106a and 106b. 
A bedplate 108 is secured to the supporting surface 102a by foundation bolts 112. In an operation state, the turbine casing thermally expands due to high temperature of steam, combustion gas and the like inside the casing. Thus, it is necessary to install the turbine casing such as to set securing points which are base points of thermal expansion and to allow thermal expansion in areas other than the securing point. Among the base points, a pair of base points disposed at an axis of the rotor shaft, on the front and back of the turbine casing, are the securing points in the direction perpendicular to the rotor shaft.
A pair of bedplates 110 are installed securely to the supporting surface 102a by the foundation bolts 112 on the axis line of the rotor shaft at the front and back of the space 104. A transverse anchor 114 projecting from each of the bedplates 110 is formed integrally with the bedplate 110. The transverse anchor 114 is fit in a key groove (not shown) provided on a bottom part of each of the bearing housing 106a and 106b so as to position and secure the turbine casing in the direction perpendicular to the rotor shaft.
FIG. 9 (FIG. 4 of Patent Literature 1) shows an axial anchor 116 embedded in the concrete frame 102. The axial anchor 116 is fitted in a hole 122 drilled in the bedplate 108. The axial anchor 116 functions as the securing point in the direction of the rotor shaft and the low-pressure turbine outer casing 105a and 105b is positioned and secured in the direction of the rotor shaft by the axial anchor.
In the proximity of the axial anchor 116, a key groove 118a is formed in the bedplate 108 and a key groove 118b is formed in the low-pressure turbine 105a or 105b. A key 120 is inserted in the key grooves 118a and 118b to position and secure the low-pressure turbine outer casing 105a or 105b to the bedplate 108 by means of the key 120. The key 120 is disposed in the direction perpendicular to the rotor shaft. This allows the thermal expansion of the low-pressure turbine outer casing 105a or 105b in the direction perpendicular to the rotor shaft.
Another example of a conventional securing apparatus for the bearing housing integrally formed in a steam turbine casing, is explained in reference to FIG. 10. FIG. 10 shows a rotor shaft 156 between a first low-pressure turbine outer casing 154 and a second low-pressure turbine outer casing 154. A first bearing housing 158 and a second bearing housing 160 are provided integrally with the first low-pressure turbine outer housing 152. A third bearing housing 162 is provided integrally with the second low-pressure turbine outer housing 154. The first to third bearing housings support the rotor shaft 156 rotatably.
A first securing apparatus 150A for the bearing housing is configured as follows. A transverse anchor 166 disposed in a vertical direction is fitted and secured to a lower wall 164 of the first bearing housing 158, the lower wall 164 is placed on a top surface of the concrete frame 168, and the transverse anchor 166 is buried in the concrete frame 168. This allows thermal expansion of the first bearing housing 158 in the direction of the rotor shaft and fixing a movement of the first bearing housing 158 in the direction perpendicular to the rotor shaft 158.
A second securing apparatus 150B for the bearing housing is configured as follows. A transverse anchor 174 disposed in a vertical direction is fitted and secured to a lower wall 170 of the second bearing housing 160 and a transverse anchor 176 disposed in the vertical direction is fitted and secured to a lower wall 172 of the third bearing housing 162. The lower walls 170 and 172 are placed on the top surface of a concrete frame 178, and the transverse anchors 174 and 176 are buried in the concrete frame 178. This allows thermal expansion of the second and third bearing housings 160 and 162 in the direction of the rotor shaft and fixing a movement of the second and third bearing housings 160 and 162 in the direction perpendicular to the rotor shaft 158.
Another securing apparatus for securing a turbine housing is disclosed in Patent Literature 2. Such securing apparatus is explained in reference to FIG. 11. The securing apparatus 200 for the turbine housing is configured such that a key groove is formed in a bottom surface of a leg 206 of a low-pressure turbine outer casing 204 and a key is formed in a top surface of a bedplate 208 and a key 210 is inserted in the key grooves. The bedplate 208 has a projection 208a formed with a key insertion groove 211. An anchor block 212 is inserted in the key insertion groove 211 via an adjusting liner 214. The anchor block 212 is welded to a hardware 216 embedded in the concrete frame 202. In this manner, by means of the anchor block 212, the bedplate 208 is secured and the low-pressure turbine outer casing is positioned and secured.